Process for producing a calcium carboxylate

ABSTRACT

A process for producing a calcium carboxylate comprising contacting a nitrile compound, a calcium compound selected from calcium hydroxide, calcium oxide or mixtures thereof, and water at a temperature of about 90° C. to about 250° C. at a sufficient pressure and for a sufficient time to produce a reaction mixture comprising calcium carboxylate.

RELATED APPLICATIONS

This application claims priority of the prior provisional applicationSer. No. 60/392,323, entitled “Process For Producing A CalciumCarboxylate” filed Jun. 27, 2002 which is hereby incorporated byreference into this application.

BACKGROUND OF THE INVENTION

This invention relates to a process for producing a calcium carboxylatefrom a nitrile compound using calcium hydroxide or calcium oxide andwater. In one aspect, this invention relates to a process for producingcalcium propionate from propionitrile and calcium hydroxide or calciumoxide.

Calcium carboxylates produced according to the process of the inventioncan be used to produce the corresponding carboxylic acids. Calciumcarboxylates also have other uses. For example, calcium acetate is usedas a thickening agent, such as in cake batters, puddings, and piefillings, as buffers in controlling pH of food during various stages ofprocessing as well as in the finished product, as a preservative toprevent microbial growth, and as a calcium supplement in pet products.In addition, calcium propionate is used on a large scale as apreservative in the foodstuffs sector, particularly in baked goods toinhibit molds and other microorganisms, and as a preservative andnutritional supplement in animal feeds.

Calcium carboxylates are typically prepared by the conventional methodsfor synthesizing carboxylic acid salts, for example by reacting acarbonate, hydroxide, or oxide with a concentrated or dilute carboxylicacid. Calcium propionate is typically produced from propionic acid andcalcium hydroxide.

U.S. Pat. No. 4,700,000 (Merkel et al.) discloses an improvement to theconventional process for producing calcium propionate from propionicacid. Merkel et al. discloses that water formed during the reaction ofcalcium hydroxide with propionic acid is removed as an azeotropicmixture of water and propionic acid. Merkel et al. discloses that thevaporous mixture of water and propionic acid advantageously used for thepreparation of calcium propionate by a process whereby this mixture ispassed into an aqueous mixture containing calcium propionate and calciumhydroxide, with or without propionic acid, during which the pH isadjusted to 5-10 by further addition of calcium hydroxide, and thecalcium propionate is isolated by crystallization.

U.S. Pat. No. 3,876,691 (Lincoln) discloses the hydrolysis of nitriteswith an aqueous solution of barium hydroxide to produce the barium saltof the carboxylic acid corresponding to the nitrile. Lincoln, however,discloses that calcium oxide was ineffective as the hydrolyzing agentand that barium hydroxide is unique in its ability to hydrolyze nitritesas compared with the other most common alkaline earth metal hydroxide,i.e. calcium hydroxide (see Example III of Lincoln).

U.S. Pat. No. 5,763,652 (Kawabe et al.) discloses the hydrolysis of anitrile compound with a basic catalyst to form a salt of a carboxylicacid and a base, wherein the basic catalyst is particularly an alkalimetal hydroxide (col. 3, lines 4-6). Kawabe et al. also discloses thehydration of a nitrile compound to the corresponding amide in thepresence of a manganese oxide catalyst. Optionally, the hydration of thenitrile compound can be conducted in the presence of a combination ofthe manganese oxide and a metallic simple substance or compoundcontaining Group Ia elements (e.g. Na, K, etc.), Group IIa elements(e.g. Mg, Ca, Ba, etc.), Group IIb elements (e.g. Zn), Group IVaelements (e.g. Zr, etc.), Group IVb elements (e.g. Sn, etc.), and GroupVa elements (e.g. V, etc.). (See col. 12, lines 26-65). Kawabe et al.further discloses that the amide compound formed by the hydration of thenitrile compound can be hydrolyzed by an inorganic base, for example,alkali metal hydroxides, alkali metal carbonates, alkali metalhydrogencarbonates, alkaline earth metal hydroxides, and alkali earthmetal carbonates, preferably alkali metal hydroxides and carbonates (seecol. 15, lines 47-57, and col. 16, lines 1-6). Kawabe et al. does notdisclose the hydrolysis of a nitrile compound with calcium hydroxide northe hydration of a nitrile compound with a calcium compound alone.

Therefore, to produce calcium propionate from propionitrile, one ofordinary skill in the art would first convert the propionitrile to thefree acid via acid or caustic hydrolysis. The acid hydrolysis wouldproduce large amounts of a byproduct ammonium salt. Typical basehydrolysis with caustic soda, i.e. sodium hydroxide, would consume largequantities of sodium hydroxide, or require capital-intensiveelectrodialysis to recover the sodium hydroxide. The acid wouldsubsequently be reacted with calcium hydroxide or calcium oxide toproduce calcium propionate. In the alternative, one of ordinary skill inthe art, based on the teaching of the Kawabe et al. patent, wouldhydrate a nitrile compound using a manganese oxide catalyst to producethe corresponding amide and then hydrolyze the amide compound using abase, e.g. calcium hydroxide.

A commercially practical process for producing calcium carboxylatesdirectly from nitrile compounds and a calcium compound has now beendiscovered.

SUMMARY OF THE INVENTION

According to the invention, a process for producing a calciumcarboxylate is provided comprising contacting a nitrile compound, acalcium compound selected from calcium hydroxide, calcium oxide ormixtures thereof, and water at a temperature of about 90° C. to about250° C. at a sufficient pressure and for a sufficient time to produce areaction mixture comprising calcium carboxylate.

Further according to the invention, ammonia is removed from the reactionmixture and the calcium carboxylate is recovered.

Still further according to the invention, a process for producing acalcium carboxylate is provided comprising (a) contacting a nitrilecompound, a calcium compound selected from calcium hydroxide, calciumoxide or mixtures thereof, and water in a reaction vessel at atemperature of about 90° C. to about 250° C. at a sufficient pressureand for a sufficient time to produce a first reaction mixture comprisingcalcium carboxylate, the amide corresponding to the nitrile compound,calcium hydroxide, water and ammonia; (b) venting the reaction vesselwith or without prior cooling to remove ammonia and produce a secondreaction mixture; (c) optionally adding additional water to the secondreaction mixture; (d) heating the second reaction mixture to a suitabletemperature to remove additional ammonia and, optionally, water from thesecond reaction mixture and hydrolyze at least a portion of the amide toproduce additional calcium carboxylate; and (e) recovering the calciumcarboxylate.

BRIEF DESCRIPTION OF THE DRAWINGS

NOT APPLICABLE.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a process for producing calcium carboxylatedirectly from a nitrile compound using a calcium compound selected fromcalcium hydroxide, calcium oxide and mixtures thereof, with the provisothat the hydrolysis of the nitrile compound with the calcium compoundcan be conducted without the presence of a separate catalyst, such as amanganese oxide catalyst.

A first embodiment of the invention relates to a process for producing acalcium carboxylate comprising contacting a nitrile compound, a calciumcompound selected from calcium hydroxide, calcium oxide or mixturesthereof, and water at a temperature of about 90° C. to about 250° C. ata sufficient pressure, i.e. a pressure sufficient to achieve the desiredtemperature, and for a sufficient time to produce a reaction mixturecomprising calcium carboxylate.

After formation of the reaction mixture comprising calcium carboxylate,the reaction mixture is typically further processed to remove ammoniafrom the reaction mixture and the calcium carboxylate is recovered.

A second embodiment of the invention relates to a preferred process forproducing a calcium carboxylate comprising (a) contacting a nitrilecompound, a calcium compound selected from calcium hydroxide, calciumoxide or mixtures thereof, and water in a reaction vessel at atemperature of about 90° C. to about 250° C. at a sufficient pressure,i.e. a pressure sufficient to achieve the desired temperature, and for asufficient time to produce a first reaction mixture comprising calciumcarboxylate, the amide corresponding to the nitrile compound, calciumhydroxide, water and ammonia; (b) optionally cooling the first reactionmixture, (c) venting the reaction vessel to remove ammonia and produce asecond reaction mixture; (d) optionally adding additional water to thesecond reaction mixture; (e) heating the second reaction mixture to asuitable temperature to remove additional ammonia and, optionally, waterfrom the second reaction mixture and hydrolyze at least a portion of theamide to produce additional calcium carboxylate; and (f) recovering thecalcium carboxylate.

Nitrile compounds that can be employed according to the inventioninclude nitrile compounds represented by the formula R—CN, wherein R isselected from an aliphatic hydrocarbon group, an alicyclic hydrocarbongroup, an aromatic hydrocarbon group, or a heterocyclic hydrocarbongroup, and wherein R is optionally substituted.

The aliphatic hydrocarbon group includes, but is not limited to,saturated hydrocarbon groups having about 1 to 12 carbon atoms,preferably about 1 to 6 carbon atoms, or unsaturated hydrocarbon groupshaving about 2 to 12 carbon atoms, preferably about 2 to 6 carbon atoms.Examples of suitable saturated aliphatic hydrocarbon groups includemethyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl,pentyl, hexyl, octyl, decyl, and the like. Examples of suitableunsaturated aliphatic hydrocarbon groups includes vinyl, allyl,1-propenyl, isopropenyl, 2-butenyl, ethynyl, 2-propynyl, and the like.

The alicyclic hydrocarbon group includes, but is not limited to,cycloalkyl and cycloalkene groups having about 3 to 10 carbon atoms.Examples of suitable alicyclic hydrocarbon groups include cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl, and cycloalkylenegroups corresponding to these cycloalkyl groups.

The aromatic hydrocarbon group includes, but is not limited to, arylgroups having about 6 to 14 carbon atoms, and alkaryl and aralkyl groupshaving about 7 to 15 carbon atoms. Examples of suitable aromatichydrocarbon groups include phenyl, naphthyl, benzyl, phenethyl, tolyl,xylyl, and the like.

The heterocyclic group includes heterocyclic groups each having at leastone atom, as a hetero atom, selected from a nitrogen atom, an oxygenatom, or a sulfur atom, and may be whichever of an aromatic heterocyclicgroup, a non-aromatic heterocyclic group, or a condensed heterocyclicgroup. Examples of suitable heterocyclic groups include furyl, thienyl,pyrrolyl, imidazolyl, pyrrolidinyl, pyridyl, pyrazinyl, pyrimidinyl,indolyl, pyridazinyl, piperidino, morpholino, morpholinyl, quinolyl, andthe like.

These groups represented by R may optionally be substituted. Examples ofsuitable substituents include halogen atoms, a hydroxyl group, alkylgroups (e.g. methyl, ethyl, propyl, isopropyl and other C₁₋₅ alkylgroups), aryl groups (e.g. phenyl, tolyl, xylyl, chlorophenyl,methoxyphenyl, naphthyl and other C₆₋₁₄ aryl groups), ether groups,alkoxy groups (e.g. methoxy, ethoxy and other C₁₋₅ alkoxy groups),aryloxy groups (e.g. phenoxy and other C₆₋₁₄ aryloxy groups), a mercaptogroup, alkylthio groups (e.g. methylthio, ethylthio and other C₁₋₅alkylthio groups), arylthio groups (e.g. phenylthio and other C₆₋₁₄arylthio groups), a carboxyl group, ester groups (e.g. methoxycarbonyland other C₁₋₆ alkoxy-carbonyl groups); acetoxy and other C₂₋₁₂ acyloxygroups, acyl groups (e.g. acetyl, benzoyl and other C₂₋₁₂ acyl groups),amino groups, including mono- or di-substituted amino groups (e.g.methylamino, dimethylamino and other mono- or di-C₁₋₅ alkylaminogroups), a nitro group, and the like. The number of such substituents tobe substituted on the R group represented may be about 1 to 4.

Examples of suitable aliphatic nitriles include acetonitrile,propionitrile, butyronitrile, isobutyronitrile, valeronitrile,isovaleronitrile, capronitrile and other saturated mononitriles;malonitrile, succinonitrile, glutaronitrile, adiponitrile,α-aminopropionitrile, α-aminomethylthiobutyronitrile,α-aminobutyronitrile, aminoacetonitrile; lactonitrile,hydroxyacetonitrile, α-hydroxyisobutyronitrile (acetocyanohydrin),α-hydroxy-γ-methylthiobutyronitrile(4-methylthio-2-hydroxybutyronitrile); cyanoacetic acid;amino-3-propionitrile, and unsaturated nitriles (e.g. acrylonitrile,methacrylonitrile, allyl cyanide, crotononitrile), and the like.

Examples of suitable alicyclic nitriles includecyclopentanecarbonitrile, cyclohexanecarbonitrile, and the like.

Examples of suitable aromatic nitriles include benzonitrile, o-, m- andp-chlorobenzonitrile, o-, m- and p-fluorobenzonitrile, o-, m- andp-nitrobenzonitrile, p-aminobenzonitrile, 4-cyanophenol, o-, m- andp-tolunitrile, 2,4-dichlorobenzonitrile, 2,6-dichlorobenzonitrile,2,6-difluorobenzonitrile, anisonitrile, α-naphthonitrile,β-naphthonitrile, phthalonitrile, isophthalonitrile, terephthalonitrile,benzyl cyanide, cinnamoyl nitrile, phenylacetonitrile, mandelonitrile,p-hydroxyphenylacetonitrile, p-hydroxyphenylpropionitrile,p-methoxyphenylacetonitrile and the like.

Examples of suitable heterocyclic nitriles include nitrile compoundseach having a heterocyclic group containing 5- or 6-membered ring andhaving at least one atom selected from a nitrogen atom, an oxygen atomor a sulfur atom as a hetero atom, such as 2-thiophenecarbonitrile,2-furonitrile, 2-cyanopyridine, 3-cyanopyridine, 4-cyanopyridine,cyanopyrazine, 5-cyanoindole, cyanopiperidine, cyanopiperazine, and thelike.

More particularly, the nitrile compound in which the aliphatichydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbongroup or heterocyclic group represented by R has a substituent, includesamino-nitrile compounds, cyanohydrin compounds and the like. Examples ofthe aminonitrile compounds include aminoacetonitrile,α-aminopropionitrile, α-aminobutyronitrile, 3-aminopropionitrile, andthe like. Examples of the cyanohydrin compounds include α-cyanohydrincompounds, ,β-cyanohydrin compounds, γ-cyanohydrin compounds and thelike. Such cyanohydrin compound may contain, for instance, about 2 to18, preferably about 3 to 12, and more preferably about 3 to 8 carbonatoms.

The suitable α-cyanohydrin compounds can be represented by the formula

wherein R¹ and R² independently represent a hydrogen atom or ahydrocarbon group which may have a substituent, and R¹ and R² may form aring together with the adjacent carbon atom, with a proviso that R¹ andR² are not concurrently hydrogen atoms.

Examples of the hydrocarbon group represented by R¹, R², and thesubstituent which the hydrocarbon group may have include the aliphatichydrocarbon groups, alicyclic hydrocarbon group, aromatic hydrocarbongroup, and the substituents which these groups may have, as describedabove for the group R.

Examples of the ring which is formed with R¹ and R² together with theadjacent carbon atom include cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, cyclooctyl, and the like.

Examples of suitable α-cyanohydrin compound include hydroxyacetonitrile,lactonitrile, acetone cyanohydrin, 2-hydroxybutanenitrile,2-hydroxy-4-methylthiobutanenitrile, 2-hydroxy-2-methylbutanenitrile,2-hydroxy-3-methylbutanenitrile, 2-hydroxy-3-butenenitrile,2-hydroxypentanenitrile, 2-hydroxyhexanenitrile, 2-hydroxyoctanenitrileand other aliphatic .alpha.-cyanohydrins;2-hydroxycyclohexaneacetonitrile, cyclopentanone cyanohydrin,cyclohexanone cyanohydrin, mandelonitrile,2-hydroxy-3-phenylbutanenitrile, and the like.

Examples of suitable β-cyanohydrin compounds include3-hydroxypropanenitrile, 3-hydroxybutanenitrile, 3-hydroxyhexanenitrile,2-hydroxycyclohexanecarbonitrile or 3-hydroxy-3-phenylpropanenitrile.

Examples of suitable γ-cyanohydrin compounds includes4-hydroxy-butanenitrile, 4-hydroxyhexanenitrile,3-hydroxyhexanecarbonitrile, 4-hydroxy-4-phenylbutanenitrile, and thelike.

The nitrile compound is preferably a compound where the salt of thecorresponding carboxylic acid is water-soluble. The currently preferrednitrile is propionitrile, which can be obtained as a byproduct of theadiponitrile manufacturing process, with the preferred calciumcarboxylate being calcium propionate.

The nitrile compounds described above can be prepared by anyconventional process known to those of skill in the art. For example, analiphatic nitrile may be prepared by reacting an alkyl halide withsodium cyanide or other alkali metal cyanide. The aromatic nitrites canbe produced by, for instance, a process comprising diazotizing an amineand allowing the resultant product to react with copper (I) cyanide, orother routes. Benzonitrile, for example, can be produced by reactingbenzoic acid with urea in the presence of a metallic catalyst. Theα-cyanohydrin compounds among such nitrile compounds may be prepared by,for example, a process which comprises allowing cyanide to react with analdehyde or a ketone, a process which comprises allowing an adductderived from an aldehyde or ketone and sodium hydrogen sulfite to reactwith an alkali cyanide such as potassium cyanide, or others. Theβ-cyanohydrin compound can be prepared by allowing an epoxide to reactwith hydrogen cyanide, for example.

Calcium compounds that can be employed according to the process of theinvention are selected from calcium hydroxide, calcium oxide, ormixtures thereof. When calcium oxide is used, the conditions of theprocess will result in at least part of the calcium oxide beinghydrolyzed to calcium hydroxide.

The amount of calcium compound employed in the process of the inventioncan conveniently be expressed as a molar ratio of calcium compound tonitrile compound charged to the reaction vessel. Broadly, the molarratio of calcium compound to nitrile compound is about 0.5:1 to about0.75:1. It is preferred to use a stoichiometric excess of calciumcompound compared to the nitrile compound, i.e. a molar ratio greaterthan 0.5:1 will result in an excess of the calcium compound. For examplea molar ratio of 0.75:1 corresponds to a molar excess of 50%. The molarratio of calcium compound to nitrile compound is preferably greater than0.5:1 to about 0.6:1 (an excess of calcium compound up to about a 20%molar excess), and most preferably about 0.505:1 to about 0.55:1 (amolar excess of about 1% to 10%).

The amount of water employed in the process of the invention is thatamount necessary to conduct the process, e.g. water needed for thehydrolysis plus water to function as the reaction solvent/diluent. Theamount of water employed in the process of the invention canconveniently be expressed as a molar ratio of water to nitrile compoundcharged to the reaction vessel. The molar ratio of water to nitrilecompound is about 5:1 to about 30:1, preferably about 8:1 to about 18:1,and more preferably about 12:1 to about 15:1.

In cases where the nitrile compound is not sufficiently soluble inwater, a co-solvent can be used to increase the solubility of thenitrile compound and improve process operation. Suitable co-solventsinclude Water-soluble organic solvents such as acetone and otherketones; methanol, ethanol and other alcohols; and ethylene glycol,glycerol and other polyols, dimethyl ether, tetrahydrofuran, dioxane andother ethers. Polyols can also aid the reaction by increasing thesolubility of calcium hydroxide. The process of the invention cangenerally be conducted at a reaction temperature of about 90° C. toabout 250° C., preferably about 120° C. to about 250° C., and morepreferably about 160° C. to about 220° C. The process of the inventioncan be conducted at any suitable pressure depending on the desiredreaction temperature and the method used for removal of ammonia from thereaction mixture. It is currently preferred to conduct the reaction at apressure at or above the autogenic pressure based on the reactiontemperature in order to maintain most of the water and the nitrilecompound in the liquid phase. Such pressure will be readily apparent toone of ordinary skill in the art without undue experimentation. Forexample, when propionitrile is used as the nitrile compound and thereaction temperature is 170° C., the autogenic pressure is about 110-120psia (about 758.4-827.4 KPa). If ammonia is to be removed during thereaction, such as continuously during the formation of the calciumcarboxylate, the pressure is preferably at or above the autogenicpressure but a pressure below the autogenic pressure may be used. If apressure below the autogenic pressure is used, it is preferred torecover and recycle any nitrile compound removed with the ammonia foroptimum operation of the process of the invention. The reaction timewill be the time suitable to obtain the desired conversion of thenitrile compound into calcium carboxylate. Generally, the reaction timewill vary depending on process parameters including the reactiontemperature and the nitrile used. The process of the invention can beconducted as a batch, semi-batch, or continuous process depending on thescale of the process and capital investment required.

After completion of the initial reaction whereby the reaction mixturecomprising the calcium carboxylate is obtained, the process furthercomprises recovering and producing a calcium carboxylate productsuitable for commercial use. As part of the recovery process, it will benecessary to remove ammonia if sufficient ammonia has not been removedduring the reaction, i.e. production of the first reaction mixture.

Ammonia removal can be conducted by any conventional method known tothose of ordinary skill in the art. One option for ammonia removal is tovent the reaction vessel vapor space following completion of theformation of the first reaction mixture. Depending on the temperatureand pressure of the first reaction, this venting procedure wouldtypically be expected to remove the majority, i.e. 55-95%, of the freeammonia. A second option is to cool the first reaction mixture to atemperature below the atmospheric boiling point, typically less than 70°C., prior to venting the headspace of the reaction vessel. This optionis preferred if the configuration of the equipment used for the firstreaction is not suitable for ammonia removal. After the venting processis completed, the remaining ammonia can be removed by heating the secondreaction mixture at the pressure after the venting step, i.e. preferablyat or near atmospheric pressure, to distill the ammonia overhead. Thetemperature that the second reaction mixture is heated to will be anysuitable temperature effective to remove the desired amount of ammoniaand will be readily apparent to those of ordinary skill in the art.Typically, the temperature is about 70° C. to about 105° C. If astraight takeover distillation is used, i.e. no rectification of thedistillate, it may be necessary to boil a significant amount of wateroverhead to remove the ammonia to very low levels. If water is to beremoved overhead, it is currently preferred to add water to the reactionmixture after the vent step and prior to the distillation. If aco-solvent is used and the boiling point of the co-solvent is such thatco-solvent is also removed during the distillation, it may be necessaryto add an amount of co-solvent back to the reaction mixture as well. Ifthis distillation to remove ammonia is conducted in the presence ofexcess calcium compound, hydrolysis of any residual amide correspondingto the nitrile compound is promoted. The time cycle for thisdistillation can be set depending on the distillation conditions and thedesired level of amide and residual ammonia in the calcium carboxylateproduct, and will be readily apparent to those of ordinary skill in theart.

After completion of the ammonia removal, it may be necessary to adjustthe concentration of the calcium carboxylate product depending on theamount of water (and potentially co-solvent) that has been removedduring the distillation to remove ammonia. Concentration adjustment maybe needed to ensure that all of the calcium carboxylate is in solution,particularly if the insoluble, excess calcium compound is to besubsequently removed by filtration. In addition, this is the currentlypreferred point of the process to adjust the concentration if the finalproduct is to be a solution.

After the ammonia removal and concentration adjustment has occurred, theproduct mixture is neutralized and, optionally, filtered/separated. Theneutralization (pH adjustment) and filtration/separation steps can beconducted by any conventional technique known to those of ordinary skillin the art. The specific neutralization and filtration/separation stepsutilized will depend on the quality of the starting materials used,impurity levels in the final product, and the desired product quality.Three possible options are described below.

The first option is currently preferred if the highest calciumcarboxylate product quality is desired. In this option, the reactionmass is filtered/separated using conventional equipment and techniquesafter the ammonia removal and concentration adjustment steps to removeexcess insoluble calcium compound, as well as any other impurities thatmay be adsorbed onto the particle surfaces, as well as any otherinsoluble materials such as insoluble magnesium salts present in thecalcium compound used, polymers formed during the reaction, etc.Following the filtration/separation step, the pH is adjusted withcarboxylic acid corresponding to the calcium carboxylate to neutralizesoluble calcium compound (forming additional calcium carboxylate) andreach the desired pH for the product.

The second option is currently preferred if it is desired to retain theraw material value of the excess calcium compound. In this option,neutralization with carboxylic acid corresponding to the calciumcarboxylate to neutralize excess calcium compound present is performed.However, with this option any adsorbed impurities may redissolve in theproduct. Filtration/separation of the neutralized product is thenconducted to remove remaining insolubles.

The third option is feasible if a solid final product is to be producedand the product quality standards are less stringent. In this option, nofiltration/separation step is conducted. The product resulting from theammonia removal and concentration adjustment steps is neutralized withcarboxylic acid corresponding to the calcium carboxylate to neutralizeexcess calcium compound present.

Options one and two are the currently preferred options.

Once any filtration/separation and neutralization operations areconducted, the filtered and neutralized calcium carboxylate product issubjected to final product processing that is dependent on the form ofthe final product desired, i.e. a solution product or a solid product.

For a solution product, the filtered and neutralized calcium carboxylateproduct optionally has the concentration adjusted by adding water orcalcium carboxylate, and a final filtration using a polishing filter orequivalent separation device may be conducted prior to product storageor packaging.

For a solid product, the filtered and neutralized calcium carboxylateproduct is recovered and dried. Recovery and drying can be doneutilizing any conventional process known to one of ordinary skill in theart. One option is to dry the solution directly to a powder using aspray dryer or by spraying onto dry particles in a fluid bed dryer. Asecond option is to crystallize the calcium carboxylate product by waterevaporation, collection on a filter or centrifuge, and final drying inany conventional solids dryer used to dry wet solids. The first optionis currently preferred unless the second option is required by productquality specifications since the second option would require recycle ordisposal of a mother liquor stream.

EXAMPLES Example 1

Propionitrile (22 g; 0.4 mol, supplied by Aldrich Chemical, 97% min),calcium hydroxide (23.2 g, 0.31 mol, supplied by Fisher Scientific,certified grade), and deionized water (81.7 g, 4.54 mol) were charged toa 350 mL, 316 stainless steel autoclave. The autoclave was closed,agitation was initiated, and the unit was pressurized to 106 psig (730.8KPa) with helium. A helium flow of 30 std cm³/min through the head spacewas established. The contents of the autoclave were heated with anelectric mantel to 161° C. over a period of 0.5 hour. The autoclavetemperature was then controlled at 160-161° C. while the autoclavepressure was maintained at 127-142 psig (979 KPa). After 1 hour at 161°C. ammonia was detected in the gas leaving the autoclave with moist pHpaper. The heat was turned off after 6.8 hours at which time ammonia wasstill detectable in the gas leaving the autoclave. The autoclave wascooled overnight and opened the next morning. The autoclave contained awhite slurry with a very strong ammonia odor. A sample of the reactionmixture was taken, diluted 1:17.3 with deionized water and analyzedusing a Thermo Separation HPLC equipped with a 250×4.60 mm Hypersil 5μC18-BDS column. The mobile phase consisted of 5% methanol with thebalance being 0.2% phosphoric acid in water. A flow rate of 1 mL/min for12 minutes was used. The calcium propionate and propionamide werequantified with a UV detector operating at 215 λ and propionitrile wasquantified with a refractive index detector. The undiluted reactorproduct was found to contain 24.2% calcium propionate, 114 ppmpropionamide, and no detectable propionitrile.

Example 2

Propionitrile (413 g, 7.5 mol, supplied by Solutia Inc., refined: 99.6%min) was charged into a one gallon 316 stainless steel autoclave througha funnel. Calcium hydroxide (305.7 g, 4.13 mol, supplied by MississippiLime, CODEX Hydrated Lime), and one-half of the total deionized watercharge (total water=1835 g, 101.9 mol) were mixed to produce a slurrywhich was charged to the autoclave-through the same funnel. Theremaining water was used to rinse the calcium hydroxide slurry containerand was charged to the autoclave through the funnel. The autoclave wasclosed and pressurized with nitrogen to 50-60 psig (344.7-413.7 KPa),the pressure relieved, and this step repeated two additional times topurge air from the system. The pressure control valve was set to 150psig (1034.2 KPa), and a nitrogen flow (200 std cm³/min) through thereactor vapor space was started. The autoclave agitator was started andthe contents were heated to 170° C. with a mixture of steam and waterunder pressure in an internal coil. Once the temperature inside theautoclave reached 170° C., the reaction was allowed to proceed for 12.33hours after which time the steam was turned off. After the temperatureof the autoclave contents dropped to 60° C., the pressure was slowlyvented to atmospheric pressure. The product slurry was then drained intoa one-gallon bottle (2380.4 grams). The slurry was analyzed by the HPLCmethod described in Example 1 and was found to contain 31.0% calciumpropionate (a quantitative yield within the accuracy of the analysis),431 ppm propionamide, and no detectable propionitrile.

The product was filtered to remove the insoluble calcium hydroxide togive a filtrate weighing 2211 grams. The bulk of the ammonia was removedon a rotary evaporator under the vacuum provided by a water aspiratorand a bath temperature of 60° C. Approximately 400 grams of deionizedwater was added to the product during the stripping of the ammonia tokeep the calcium propionate in solution. To remove the last traces ofammonia and hydrolyze most of the residual propionamide an additional300 grams of deionized water and 1.0 grams of calcium hydroxide wasadded. Approximately 300 grams of water and ammonia was removed byatmospheric distillation with a final base temperature of 103° C. Waterwas added to dissolve all of the calcium propionate. This solution wasfiltered to obtain 2466 grams of solution containing 29.3% calciumpropionate (a quantitative yield within the accuracy of the analysis),112 ppm of propionamide, and no detectable ammonia. This material wascombined with similar material from two additional hydrolysis reactions.The pH of the combined solution was adjusted to 8.1 with propionic acid(supplied by Aldrich, 99% min). Approximately 20% of the water wasremoved by atmospheric distillation. This produced a slurry from whichthe bulk of the water was removed on a rotary evaporator. The wet solidwas dried in a vacuum oven at 60° C. and 125 mm of Hg for 24 hours toproduce a dry white solid. This material assayed as 90.6% calciumpropionate, 9.1% water and 200 ppm propionamide.

Example 3

Propionitrile (311.5 g, 5.66 mol, supplied by Solutia Inc., refined:99.6% min) was charged into a one gallon 316 stainless steel autoclavethrough a funnel. Calcium hydroxide (229.3 g, 3.09 mol, supplied byMississippi Lime, CODEX Hydrated Lime), and deionized water (1007.2 g,55.9 mol) were mixed to produce a slurry and charged to the autoclavethrough the same funnel. A second portion of deionized water (345.1 g,19.2 mol) was used to rinse the calcium hydroxide slurry container andwas charged to the autoclave through the funnel. The autoclave waspressurized with nitrogen to 45-55 psig (310.3-379.2 KPa), and thepressure relieved to under 25 psig (172.4 KPa). This cycle was repeatedtwo additional times to purge most of the air from the system. Thepressure control valve was set to 260 psig (1792.6 KPa), and a nitrogenflow (100 std cm³/min) through the reactor vapor space was started. Theautoclave agitator was started and the contents were heated to 200° C.with a mixture of steam and water under pressure in an internal coil.After the autoclave contents had been at 200° C. for one hour, thenitrogen flow was increased to 200 cm³/min to improve the control of theautoclave pressure. After the autoclave contents had been at 200° C. fora total of two hours, the steam was turned off and the reactor pressurewas released through a vapor line heated to over 200° C. over a periodof 40 minutes. The water and ammonia that flashed from the autoclave wastrapped by passing it into a scrubber containing 4862.6 grams of icewater. This scrubber solution weighed 5414.9 grams after all of theautoclave pressure had been released. After the autoclave contents hadcooled to less than 60° C. they were drained and weighed (925.1 g).Deionized water (237.2 g) was added to dissolve all of the calciumpropionate. This diluted product was analyzed by the HPLC methoddescribed in Example 1 and found to contain 28.0% calcium propionate(326 g, 1.75 mol, 62% yield), 119 ppm of propionamide, and no detectablepropionitrile. The scrubber solution was found to contain 0.34% calciumpropionate and 1.58% ammonia. From the amount of calcium propionate inthe scrubber, it was concluded that approximately 66.4 grams of theproduct was carried into the scrubber by entrainment and that 400 gramsof water and 85.5 grams of ammonia were flashed from the autoclave. Thisrepresents 90% of the ammonia that would be expected from completehydrolysis of the propionitrile charged to the autoclave. No attempt wasmade to quantify the amount of calcium propionate remaining in thereactor after the product was drained.

Example 4

A slurry of calcium hydroxide (23.4 g, 0.316 mol, supplied byMississippi Lime, CODEX Hydrated Lime) in deionized water (148 g, 8.2mol) was charge to a 300 mL Hastelloy autoclave which was equipped witha water cooled reflux condenser. The autoclave was pressurized withnitrogen to 235 psig (1620.3 KPa), and the pressure relieved to 10 psig(68.9 KPa). This cycle was repeated two additional times to purge mostof the air from the system. The autoclave was then pressurized to 235psig (1620.3 KPa) and a steady flow of 50 std cm³/min of nitrogen wasestablished across the top of the reflux condenser. After the autoclavecontents were heated to 200° C., propionitrile (43.3 mL, 33.8 g, 0.615mol, supplied by Solutia Inc., refined: 99.6% min) was injected over aperiod of two hours with a high-pressure syringe pump. The gas leavingthe unit was passed through a water scrubber to trap any propionitrile,ammonia, and water escaping the autoclave. Samples of the reactorcontents were pulled after the addition of propionitrile was complete,and then one and two hours later. The water in the gas scrubber was alsodrained, weighed, and replaced with fresh deionized water when eachsample was pulled. The reactor contents were analyzed and scrubbersamples for propionitrile, propionamide, and calcium propionate by theHPLC method described in Example 1. No calcium propionate orpropionamide was found in the scrubber samples indicating thatentrainment of the liquid contents of the autoclave into the gas did notoccur. The ammonia in the scrubber samples was also determined bytitration with 0.1 N HCl. From this data, the following time profile ofthe weight percent of propionitrile, propionamide and calcium propionateas well as the moles of propionitrile and ammonia leaving the autoclavein the gas were calculated. These results are tabulated below:

Pro- Pro- Calcium Pro- Am- Time pionitrile pionamide pionate pionitrilemonia (hours) (weight %) (weight %) (weight %) (mol) (mol) 2 1.06% 0.35% 26.1% 0.0001 0.0012 3 0.00% 0.13%  26.9% 0.0000 0.0148 4 0.00% 0.08%27.35% 0.0000 0.0116

We claim:
 1. A process for producing a calcium carboxylate comprisingcontacting a nitrile compound, a calcium compound selected from calciumhydroxide, calcium oxide or mixtures thereof, and water at a temperatureof about 90° C. to about 250° C. at a sufficient pressure and for asufficient time to produce a reaction mixture comprising calciumcarboxylate.
 2. The process of claim 1 wherein said nitrile compound isrepresented by the formula R—CN wherein R is selected from an aliphaticgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, ora heterocyclic group, and wherein R is optionally substituted.
 3. Theprocess of claim 2 wherein said R is an aliphatic hydrocarbon group. 4.The process of claim 3 wherein said nitrile is propionitrile.
 5. Theprocess of claim 1 wherein the molar ratio of calcium compound tonitrile compound is about 0.5:1 to about 0.75:1.
 6. The process of claim5 wherein the molar ratio of calcium compound to nitrile compound isgreater than 0.5:1 to about 0.6:1.
 7. The process of claim 1 wherein themolar ratio of water to nitrile compound is about 5:1 to about 30:1. 8.The process of claim 7 wherein the molar ratio of water to nitrilecompound is about 12:1 to about 15:1.
 9. The process of claim 1 furthercomprising removing ammonia from said reaction mixture.
 10. The processof claim 9 further comprising recovering said calcium carboxylate. 11.The process of claim 1 wherein said temperature is about 160° C. toabout 220° C.
 12. The process of claim 1 further comprising removingammonia from said reaction mixture, and subsequently recovering thecalcium carboxylate.
 13. A process for producing a calcium carboxylatecomprising (a) contacting a nitrile compound, a calcium compoundselected from calcium hydroxide, calcium oxide or mixtures thereof, andwater in a reaction vessel at a temperature of about 90° C. to about250° C. at a sufficient pressure and for a sufficient time to produce afirst reaction mixture comprising calcium carboxylate, the amidecorresponding to said nitrile compound, water and ammonia; (b)optionally cooling the first reaction mixture; (c) venting the reactionvessel to remove ammonia and produce a second reaction mixture; (d)optionally adding additional water to the second reaction mixture; (e)heating said second reaction mixture to a suitable temperature to removeadditional ammonia and, optionally, water from the second reactionmixture and hydrolyze at least a portion of said amide to produceadditional calcium carboxylate; and (f) recovering the calciumcarboxylate.
 14. The process of claim 13 wherein said nitrile compoundis represented by the formula R—CN wherein R is selected from analiphatic group, an alicyclic hydrocarbon group, an aromatic hydrocarbongroup, or a heterocyclic group, and wherein R is optionally substituted.15. The process of claim 14 wherein said R is an aliphatic hydrocarbongroup.
 16. The process of claim 15 wherein said nitrile ispropionitrile.
 17. The process of claim 13 wherein the molar ratio ofcalcium compound to nitrile compound is about 0.5:1 to about 0.75:1. 18.The process of claim 17 wherein the molar ratio of calcium compound tonitrile compound is greater than 0.5:1 to about 0.6:1.
 19. The processof claim 13 wherein the molar ratio of water to nitrile compound addedin step (a) is about 5:1 to about 30:1.
 20. The process of claim 19wherein the molar ratio of water to nitrile compound added in step (a)is about 12:1 to about 15:1.
 21. The process of claim 13 wherein saidtemperature is about 160° C. to about 220° C.
 22. The process of claim13 wherein said calcium carboxylate is recovered by (i) adjusting theconcentration of the product of step (e), (ii) filtering to removeinsoluble, unreacted calcium compound, (iii) adding carboxylic acidcorresponding to the nitrile compound to neutralize any soluble calciumcompound and produce a neutralized product, and (iv) optionallyfiltering the neutralized product to remove insolubles and produce aneutralized solution product.
 23. The process of claim 22 furthercomprising drying the neutralized solution product to produce solidcalcium carboxylate.
 24. The process of claim 13 wherein said calciumcarboxylate is recovered by (i) adjusting the concentration of theproduct of step (e), (ii) adding carboxylic acid corresponding to thenitrile compound to neutralize remaining calcium compound and produce aneutralized product, and (iii) optionally filtering the neutralizedproduct to remove insolubles and produce a neutralized solution product.25. The process of claim 24 further comprising drying the neutralizedsolution product to produce solid calcium carboxylate.
 26. The processof claim 13 wherein said first reaction mixture is cooled prior to saidventing in step (c).
 27. A process for producing a calcium propionatecomprising contacting propionitrile, a calcium compound selected fromcalcium hydroxide, calcium oxide or mixtures thereof, and water at atemperature of about 90° C. to about 250° C. at a sufficient pressure toachieve the desired temperature and for a sufficient time to produce areaction mixture comprising calcium propionate; wherein the molar ratioof calcium compound to propionitrile is about 0.5:1 to about 0.75:1, andthe molar ratio of water to propionitrile is about 5:1 to about 30:1.28. The process of claim 27 wherein the molar ratio of calcium compoundto propionitrile is greater than 0.5:1 to about 0.6:1.
 29. The processof claim 27 wherein the molar ratio of water to nitrile compound isabout 12:1 to about 15:1.
 30. The process of claim 27 wherein saidtemperature is about 160° C. to about 220° C.
 31. The process of claim27 further comprising removing ammonia from said reaction mixture. 32.The process of claim 31 further comprising recovering said calciumpropionate.
 33. The process of claim 27 further comprising removingammonia from said reaction mixture, and subsequently recovering thecalcium propionate.
 34. A process for producing a calcium propionatecomprising (a) contacting a propionitrile, a calcium compound selectedfrom calcium hydroxide, calcium oxide or mixtures thereof, and water ina reaction vessel at a temperature of about 90° C. to about 250° C. at asufficient pressure and for a sufficient time to produce a firstreaction mixture comprising calcium propionate, the propionamide, waterand ammonia; (b) optionally cooling the first reaction mixture; (c)venting the reaction vessel to remove ammonia and produce a secondreaction mixture; (d) optionally adding additional water to the secondreaction mixture; (e) heating said second reaction mixture to a suitabletemperature to remove additional ammonia and, optionally, water from thesecond reaction mixture and hydrolyze at least a portion of said amideto produce additional calcium propionate; and (f) recovering the calciumpropionate wherein the molar ratio of calcium compound to propionitrileis about 0.5:1 to about 0.75:1, and the molar ratio of water topropionitrile is about 5:1 to about 30:1.
 35. The process of claim 34wherein said calcium propionate is recovered by (i) adjusting theconcentration of the product of step (e), (ii) filtering to removeinsoluble, unreacted calcium compound, (iii) adding a propionic acid toneutralize any soluble calcium compound and produce a neutralizedproduct, and (iv) optionally filtering the neutralized product to removeinsolubles and produce a neutralized solution product.
 36. The processof claim 35 further comprising drying the neutralized solution productto produce solid calcium propionate.
 37. The process of claim 34 whereinsaid calcium propionate is recovered by (i) adjusting the concentrationof the product of step (e), (ii) adding propionic acid to neutralizeremaining calcium compound and produce a neutralized product, and (iii)optionally filtering the neutralized product to remove insolubles andproduce a neutralized solution product.
 38. The process of claim 37further comprising drying the neutralized solution product to producesolid calcium propionate.
 39. The process of claim 34 wherein saidtemperature is about 160° C. to about 220° C.
 40. The process of claim34 wherein said first reaction mixture is cooled prior to said ventingin step (c).